Is it a good idea to run purge every hour?

The only reason you'd need to run Purge is if you're issuing a ton of delete/update commands. Otherwise, there's no point whatsoever.

As @Vertica_Curtis indicates, it's best to avoid manual purges They can run for a very long time!

Take a look at the PurgeMergeoutPercent configuration parameter:

verticademos=> SELECT default_value, description FROM configuration_parameters WHERE parameter_name = 'PurgeMergeoutPercent';
 default_value |                                       description
---------------+------------------------------------------------------------------------------------------
 20            | Maximum % of rows that may be deleted before Tuple Mover purges the ROS through mergeout
(1 row)

If you want Vertica to be more assertive on purging data automatically, you can try lowering the percentage to between 5 and 10. Do not go below 5, though! Setting PurgeMergeoutPercent value low will aggressively qualify ROS containers for purge operation and that will have significant impact on system resources!!!